Process for preparing polyurethane-backed substrate

Abstract

Substrates having successive layers of a cellular polyurethane and a noncellular polyurethane are prepared using certain siloxane-polyether block copolymers in the noncellular polyurethane formulation. The use of the block copolymer reduces or eliminates the formation of a bubble line at the interface of the polyurethane layers, thereby improving physical and cosmetic properties of the carpet.

What is claimed is: 
     
       1. A process for preparing a polyurethane backed substrate, comprising applying to a substrate a first layer of a polyurethane-forming composition and applying to said first layer a second layer of a polyurethane forming composition and curing said layers, wherein one of said first and second layers is a non-cellular polyurethane composition, and the other of said first and second layers is a cellular polyurethane composition, and   wherein said non-cellular polyurethane composition contains about 0.03 to about 2.0 weight percent of a polysiloxane-polyether block copolymer, said block copolymer containing about 10 to about 30 weight percent dialkylsiloxane units, about 30 to about 70 weight percent oxyethylene units and about 0 to about 55 weight percent other oxyalkylene units.   
     
     
       2. The process of claim 1 wherein said polysiloxane-polyether block copolymer contains dimethylsiloxane and oxypropylene groups and has a dimethylsiloxane content of about 15 to about 25 percent, an oxyethylene content from about 30 to about 50 percent, and an oxypropylene content from about 30 to about 55 percent. 
     
     
       3. The process of claim 2 wherein said noncellular polyurethane composition comprises a polyether polyol having an equivalent weight from about 1000 to about 5000 and an aromatic polyisocyanate. 
     
     
       4. The process of claim 3 wherein said noncellular polyurethane composition comprises (a) a polymer or copolymer of propylene oxide having an equivalent weight from about 1000 to about 2500, an average functionality for about 1.8 to about 2.2, (b) TDI, MDI or a prepolymer or derivative thereof and (c) about 30 to about 225 parts by weight of an inorganic filler, per 100 parts by weight polyether polyol. 
     
     
       5. The process of claim 3 wherein said cellular polyurethane composition comprises a polyether polyol having an equivalent weight from about 1000 to about 5000, and an aromatic polyisocyanate. 
     
     
       6. The process of claim 5 wherein said cellular polyurethane composition comprises (a) polymer or copolymer of propylene oxide having an average functionality from about 1.8 to about 2.1 and an average equivalent weight from about 1000 to about 2500, (b) TDI, MDI or a prepolymer or derivative thereof and a sufficient quantity of a blowing agent to provide the cellular polyurethane with a density from about 0.2 to about 0.6 pounds/cubic foot. 
     
     
       7. The process of claim 2 wherein said noncellular polyurethane composition contains a relatively high equivalent weight active hydrogen-containing material and about 0.1 to about 0.5 parts of said block copolymer per 100 parts by weight relatively high equivalent weight active hydrogen-containing material. 
     
     
       8. The process of claim 6 wherein non-cellular polyurethane composition contains about 0.1 to about 0.5 part of said block copolymer per 100 parts by weight of said polyether polyol. 
     
     
       9. The process of claim 7 wherein said substrate is a textile. 
     
     
       10. The process of claim 8 wherein said substrate is a textile. 
     
     
       11. A substrate having attached thereto successive polyurethane layers, wherein one of such layers is a cellular polyurethane which is attached directly to a non-cellular polyurethane layer containing about 0.03 to about 2.0 weight percent of a polysiloxane-polyether block copolymer, said block copolymer containing about 10 to about 30 weight percent dialkylsiloxane units, about 30 to about 70 weight percent oxyethylene units and about 0 to about 55 weight percent other oxyalkylene units. 
     
     
       12. The substrate of claim 11 wherein said dialkylsiloxane units are dimethylsiloxane units, said other oxyalkylene units are oxypropylene units, said block copolymer contains about 15 to about 25 weight percent dimethylsiloxane units, about 30 to about 45 weight percent oxyethylene units and about 40 to about 55 weight percent oxypropylene units, and said block copolymer has a molecular weight from about 10,000 to about 50,000.